1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to an optically compensated bend (OCB) liquid crystal display controlled to prevent breaking of the bending alignment of the OCB liquid crystals.
2. Description of the Related Art
A liquid crystal display is one of the most widely used among types of flat panel displays. The liquid crystal display includes two sheets of display panels in which field generating electrodes, such as pixel electrodes and common electrodes, are formed, and a liquid crystal layer interposed between the display panels. The liquid crystal display applies a voltage to the field generating electrode in order to generate an electric field in the liquid crystal layer, determines the direction of liquid crystal molecules of the liquid crystal layer based on the electric field, and displays an image by controlling the polarization of incident light.
A variety of methods have been proposed in order to improve the response speed and reference viewing angle of LCD displays. For example, there are liquid crystal displays using an optically compensated bend (OCB) method. An OCB mode LCD includes an alignment layer formed on each substrate, and the alignment layers provide a force to align the liquid crystal molecules in a direction substantially parallel to the two substrates. Also, since the liquid crystal molecules move in the same orientation when the LCD is operated, a wide viewing angle and a fast response time are realized.
In the liquid crystal display employing the OCB method, when an electric field is applied between the two field generating electrodes, orientations of liquid crystal molecules become variously oriented from a horizontal arrangement to a vertical arrangement until they reach from the substrate surface to the central surface (the arrangement of liquid crystal molecules being symmetrical to the central plane between two substrates). Therefore, a wide reference viewing angle can be obtained. To obtain such a bent alignment of the liquid crystal molecules, a horizontal alignment agent that is oriented in the same direction is used and a high voltage is initially applied. To obtain the varying alignment of the liquid crystal molecules, the alignment layer on each of the two substrates undergoes an alignment process such as rubbing in one direction. Then a high voltage is applied so as to produce a bending alignment.
If the voltage falls below a predetermined value, however, the bending alignment of the liquid crystal layer may be broken.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.